I find myself with a couple of extra rolls of PLA, one nice one having come with my new M2. I used Makergear's PLA to become familiar with my new printer. My 18 months of experience with PLA and my earlier printer shows that it is true that PLA absorbs moisture and becomes brittle making it unreliable to print with. It looks like re-vacuum bagging the idle rolls with a silica packet might be the way to go and having a pretty good vacuum pump makes this idea even more attractive. Has anyone here done this, and if so what did you use for bags?

The reason this is pertinent is I've ordered a roll of ABS and one of PETG to experiment with.

It seemed reasonable to me, so I started storing my PLA in vacuum bags with a couple silica gel packets in each. (The bags come with a small hand pump. Only thing I don't like about them is the size .. I couldn't find anything similar that was smaller, so I just stick a couple rolls in each medium-sized bag).

I don't have any evidence yet as to the efficacy of this approach, but based on reading and user comments it seemed sensible to give it a try, mimicking how the products are shipped.

My guess is they wouldn't, and think I'd even be wary of using an active approach (filament dryer) to 'restore' a spool of compromised filament. Maybe I'm just overly cautious, but I've just bit the bullet and picked up new product whenever I've had some suspect (old, improperly stored, brittle, crackling, etc.) rolls. There are a lot of variables to getting good prints, and if I can at least minimize the filament element, this seems like a worthwhile thing to do.

.. but it would be interesting to learn what success others might have had.

I use ziplock 1 gallon bags with ~6 no name silica packs (amazon: 50 packs cost ~$8 and are reusable). These are inside a trash bag with a damp rid tub. That's in a plastic bin. Works fine for at least 3 months (longer if you switch damp rid tubs).

I'd advise against trying to "rehab" brittle PLA. I got a donated "Ditto +" working again for a local group I'm a member of a while ago. The second thing I had to do was throw out all the PLA that was included. The risk of failed prints/hot end problems wasting your time are not worth any PLA I've spent money on.

They are just under ~ 18" x 24". That's still a bit large, but not quite as bad as 20" x 28".

I have a bunch of rectangular perforated aluminum 40 gram silica gel canisters that I use to keep tools from rusting. I've started using them with my filament. For now I'm just using ziplock bags, but I think I will order some of the vacuum bags. The advantage over the cloth/paper desiccant packs is that they have an indicator to tell when they are no longer working, and a couple hours in a 300 degree oven will rejuvenate them. They are available from Amazon, but there a lots of them for sale on eBay.

when we lived on the boat we used vacuum bags to reduce storage space demand. We probably didn't do it right because they seemed to expand over 3 months.

I was driven to thinking about a vacuum pump by the impressive job Esun does on their spools. I suppose sourcing the bags they use could be tricky and of course those can't be reused.
In the scheme of things PLA is cheap enough that storing half a spool probably is crazy, but "Waste not, Want not" was beaten into me at an early age.

It occurs to me that Esun may shrink wrap. If they do, I wonder how they seal it.

I bought some "airtight" plastic bins from Target that have blue foam around the lid. Using a PVC pipe to hold the spools, I can fit four in one bin. The filament leaves the tub through PTFE tubes attached to the lid. I dumped silica gel beads about an inch thick on the bottom and they have yet to turn after 7 months. Here's what I based mine off of: https://www.thingiverse.com/thing:814597